EP3027998B1 - Evaporator heat exchanger - Google Patents

Description

The present invention relates to an evaporator heat exchanger for evaporating liquid working medium according to the preamble of claim 1.

Such a heat exchanger is known from DE 20 2010 015374 U1 ,

To further reduce the fuel consumption of commercial vehicles and passenger cars is trying to regain some of the energy of the exhaust gas. This can be done thermally, ie the energy of the exhaust gas is used for example for heating a passenger compartment or for heating the internal combustion engine or the transmission. In a variant that has been discussed for some time now, although thermal energy is also taken from the exhaust gas, it is returned to the internal combustion engine in mechanical form. This method is based on a steam power process in which a particular working fluid is vaporized and overheated in an evaporator and expanded in an adjoining expander, such as a turbine, thereby generating mechanical energy. The evaporation takes place by means of heating via the exhaust gas. The working medium to be evaporated is usually first heated in an evaporator to boiling temperature, then evaporated and then superheated. This can be done in principle in two different locations in a motor vehicle. On the one hand, in an evaporator which is used instead of an exhaust gas cooler, heat can be extracted from the exhaust gas in order to evaporate the working medium. In this case, the exhaust gas is cooled by the evaporation of the fluid to be evaporated and then returned to the engine together with the fresh air. On the other hand, the main exhaust gas stream should also be used as a heat source in order to evaporate working medium in a so-called main exhaust gas evaporator. Such a main exhaust gas evaporator is usually from the vehicle manufacturers behind the muffler or behind the entire exhaust aftertreatment arranged in the exhaust system. Alternatively, the charge air can be used as a heat source in turbocharged engines.

From the WO 2012/010349 A1 is a generic evaporator heat exchanger for vaporizing liquid working fluid and the use of waste heat of an internal combustion engine known. In the known system, an introduction of the working medium into the combustion air supplied to the internal combustion engine should be substantially ruled out due to a leak or leakage at the evaporator heat exchanger. For this purpose, at least one first flow channel is formed by at least one first limiting component and at least one second flow channel of at least one second limiting component, wherein at least one of these limiting components is a fluid-conducting connection in the environment or in a receiving space, so that at a leakage at the boundary components Working medium in the environment or in the receiving space can be introduced.

Prior art concepts of a gas-fired evaporator heat exchanger contemplate reducing the risk of mixing gas and working fluid. For example, if a fluorinated refrigerant flows into the exhaust gas and is supplied to the internal combustion engine and burned in the latter, hydrofluoric acid is produced, which can escape from an exhaust pipe and cause damage there. If, for example, an alcohol is used instead of this refrigerant, the alcohol in the internal combustion engine would be burned with a leak, which would be noticeable by a sudden increase in the power of the internal combustion engine. This may be difficult to handle, especially for inexperienced drivers. The present invention therefore deals with the problem of providing an improved embodiment for an evaporator heat exchanger of the generic type, in which an undesired mixing of working medium and gas, in particular exhaust gas or charge air, can be excluded.

This problem is solved according to the invention by the subject matter of the independent claim. Advantageous embodiments are the subject of the dependent claims.

The present invention is based on the general idea of providing a leakage channel or leakage space between a first flow channel carrying a working medium and a second, gas, in particular exhaust gas or charge air, leading flow channel, thereby passing through both the first flow channel and the leakage channel or leakage space form two cover plates and an interposed and profiled fluid disk in a particularly simple design manner. The evaporator heat exchanger according to the invention for evaporating liquid working medium in this case has a housing in which said first flow channel for passing the working medium and the second flow channel for passing the gas are arranged. By a heat transfer from the gas, for example, charge air or exhaust gas to the working medium, an evaporation of the same, whereby this can then be relaxed in an expansion machine, for example in a turbine, and thereby performs mechanical work. As mentioned, according to the invention, the first flow channel and at least one leakage channel and / or leakage space are formed by two comparatively strong cover plates and a fluid disk arranged therebetween, whereby a disk package formed from two cover plates and an intermediate fluid disk thus forms the first flow channel and the at least one fluidly separated from it leakage channel or leakage chamber accommodated. The connection between the two cover plates and the interposed fluid disc is cohesively, for example via a solder joint. In each case a second flow channel is arranged between two adjacent disk packages, in which the heat-transferring gas, for example exhaust gas or charge air, flows. In the case of a fracture of the fluid disk and / or in the event of a failure of the solder seam between the fluid disk and the cover plate, the working medium passes from the first flow channel into the leakage channel or into the leakage space and can be removed therefrom without any direct mixing with it the gas flowing in the second flow channel, for example, exhaust gas leads. In the same way, the leakage channel or the leakage chamber can also be used for discharging gas escaping undesirably from the second flow channel, if, for example, loosening a solder connection between the fluid disk and the cover plate or breaking a wall of the fluid disk leads to a fluidic connection between would lead to the leakage channel and the second flow channel. As a result of this, the gas now flowing into the leakage channel or into the leakage chamber can be removed, thereby avoiding direct mixing with the working medium in the first flow channel. The leakage channel or the leakage chamber thus forms a natural, lying between the two flow channels safety barrier. The leakage channel or the leakage chamber is usually filled with air.

Suitably, the strength of a material of the fluid disk is less than the strength of a cover plate arranged on the fluid disk. This causes a kind of predetermined breaking point of the fluid disk, so that when the evaporator heat exchanger is overloaded in the region of the first flow channel, a passage of the working medium guided in the first flow channel takes place into the leakage channel. For example, breaks the fluid disk and expands Under circumstances, the cover plate delimiting the first flow channel and upsets the rib structure arranged, for example, in the second flow channel. When stretching the cover plate, a solder seam connecting the fluid disk with this cover plate can thereby be released, whereby a fluidic connection is created between the first flow channel and the leakage channel. From this, the working medium can be removed without mixing with the gas flowing in the second flow channel. In the same way, such a predetermined breaking point can also be formed by a smaller wall thickness or material thickness of the fluid disk in comparison to the cover plates connected thereto. It is always important that, in the event of an overload, the fluid disk first breaks or tears and not the cover plates. In this way, regardless of the type of failure, it can always be ensured that the leakage channel or leakage chamber located between the first and the second flow channel can be used to discharge the working medium or the gas. The leakage channel or the leakage chamber are preferably embossed circumferentially on the fluid disk, larger areas being designated as a leakage space and a smaller one as a leakage channel.

In a further advantageous embodiment of the solution according to the invention, the evaporator heat exchanger has a plurality of stacked disk packages, each with a second flow channel arranged therebetween, the leakage channel and / or the leakage space of a fluid disk having a first opening and a plurality of opposing cover plates of two adjacent disk packages each having a second opening , wherein between the second openings a leakage bush to form a (leakage) outlet channel is arranged. In this way, the leakage fluid or gas can be reliably discharged from the second flow channel or the working medium from the first flow channel.

In an advantageous development of the solution according to the invention, the housing has a housing opening, which is connected via a housing cover bushing to the first or the second opening in the cover plate of a disk package arranged adjacent to the housing. The housing cover bushing and all other leakage bushings thereby form an outlet channel, also called leakage outlet channel, for the passage of the leakage fluid, wherein on the housing cover bushing a line in the environment or periphery can be attached, in whose area a sensor is arranged, for measuring the pressure and / or the flow and / or a chemical composition of the fluid is formed in the conduit. In the outlet channel usually the ambient air pressure prevails. At the same time air is present with usual nature. If, due to an overload, the fluid disk breaks and / or tears and thus an outlet of working medium from the first flow channel or gas from the second flow channel into the leakage channel, the pressure, the temperature and / or the pressure change in this chemical composition, since the leakage fluid, whether exhaust or working fluid, other physical and / or chemical properties than air. If a corresponding change is detected by the sensor, which indicates a leak, it can for example control a pump or an exhaust gas recirculation valve conveying the working medium as a function of the signal detected by the sensor. Also conceivable is the output of a warning signal, which indicates a user of the motor vehicle visually and / or acoustically on a malfunction of the evaporator heat exchanger. As described above, the ambient air pressure of approximately 1 bar is usually applied to the sensor. If the evaporator heat exchanger is put into operation, the pressure in the leakage channel or in the leakage chamber rises due to the temperature-induced expansion to about 1-1.5 bar, which is normal. However, if the pressure does not rise, then either the sensor is defective or else the leakage channel or leakage chamber has a leak, via which a pressure reduction takes place can. If the pressure increases significantly during operation of the evaporator heat exchanger, this usually indicates a leakage of the first flow channel or of the second flow channel. The operation of the leakage channel is thus checked at each restart of the motor vehicle, in particular at each cold start.

Other important features and advantages of the invention will become apparent from the dependent claims, from the drawings and from the associated figure description with reference to the drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Preferred embodiments of the invention are illustrated in the drawings and will be described in more detail in the following description, wherein like reference numerals refer to the same or similar or functionally identical components.

Fig. 1

eine Ansicht auf einen erfindungsgemäßen Verdampferwärmeübertrager,

Fig. 2

eine Schnittdarstellung durch den Verdampferwärmeübertrager im Bereich von ersten und zweiten Strömungskanälen in intaktem Zustand,

Fig. 3

eine Darstellung wie in Fig. 2, jedoch bei gebrochener Fluidscheibe und Übertritt von Arbeitsmedium in einen Leckagekanal,

Fig. 4

eine Darstellung wie in Fig. 3, jedoch bei einem Übertritt von Gas aus dem zweiten Strömungskanal in den Leckagekanal,

Fig. 5

eine mögliche Ausführungsform der erfindungsgemäßen Fluidscheibe,

Fig. 6

eine Explosionsdarstellung des Verdampferwärmeübertragers,

Fig. 7

eine Schnittdarstellung durch den Verdampferwärmeübertrager im Bereich des Fluidein- oder -austritts,

Fig. 8

eine Darstellung wie in Fig. 7, jedoch im Bereich eines Austrittskanals für Leckagefluid,

Fig. 9

ein Druck-Zeit-Diagramm mit unterschiedlichen Kurven, die auf unterschiedliche Betriebszustände bzw. Leckagen des erfindungsgemäßen Verdampferwärmeübertragers hinweisen.

Show, in each case schematically,

Fig. 1

a view of an evaporator heat exchanger according to the invention,

Fig. 2

a sectional view through the evaporator heat exchanger in the region of first and second flow channels in the intact state,

Fig. 3

a representation like in Fig. 2 but with a broken fluid disk and transfer of working fluid into a leakage channel,

Fig. 4

a representation like in Fig. 3 but with a transfer of gas from the second flow channel into the leakage channel,

Fig. 5

a possible embodiment of the fluid disk according to the invention,

Fig. 6

an exploded view of the evaporator heat exchanger,

Fig. 7

a sectional view through the evaporator heat exchanger in the fluid inlet or outlet area,

Fig. 8

a representation like in Fig. 7 but in the region of an outlet channel for leakage fluid,

Fig. 9

a pressure-time diagram with different curves that indicate different operating conditions or leaks of the evaporator heat exchanger according to the invention.

According to the Fig. 1 , Has an inventive evaporator heat exchanger 1 for evaporating liquid working medium 2 (see also Fig. 2 to 4 ), a housing 3, in which a first flow channel 4 for passing the working medium 2 and a second flow channel 5 for passing a gas 6 are arranged. A heating of the working medium 2 takes place by a heat transfer of the gas 6, for example, exhaust gas or charge air. According to the first flow channel 4 is now formed by two cover plates 7 and 8 and an interposed and profiled fluid disk 9, wherein the fluid disk 9 together with the two cover plates 7 and 8 at least one of the two flow channels 4, 5 separate leakage channel 10 and leakage chamber 11 limited. The two cover plates 7, 8 together with a fluid disk 9 arranged therebetween form a disk pack 12, as described, for example, in accordance with FIGS Fig. 2 to 4 illustrated illustrated. The respective leakage channel 10 and the leakage chamber 11 are arranged laterally next to or at the edge of the first flow channel 5, as in particular the Fig. 5 can be seen.

The leakage channel 10 according to the invention creates a barrier between the two flow channels 4, 5, so that no direct mixing of the working medium 2 with the gas 6 and thus damage to an internal combustion engine can take place. In the evaporator heat exchanger known from the prior art, the working fluid to be evaporated flows into the exhaust gas in the event of leakage and, if, for example, a fluorinated refrigerant, such as e.g. R245fa is burned in the internal combustion engine, which produces toxic hydrofluoric acid. This would leak at the exhaust and could cause damage there. If, instead of such a refrigerant, alcohol, e.g. Ethanol or methanol used, it would be burned in a leakage of this in the internal combustion engine, which would be reflected in a sudden increase in power of the engine. In particular, inexperienced drivers would be exposed to an increased risk of accidents. Due to the barrier according to the invention in the manner of the leakage channel 10 or the leakage space 11, however, a mixing of the gas 6 with the working medium 2 can be reliably prevented in the event of virtually any failure of the fluid disk 9.

In addition to the provision of the leakage channel 10 and the leakage chamber 11 (see also Fig. 5 ), the strength of the material for the fluid disk 9 is less than the strength of the cover plates 7, 8 connected to the fluid disk 9, so that the Fluid disk 9 generally represents a kind of predetermined breaking point in the system of the disk package 12. Similarly, such a predetermined breaking point can also be realized by a smaller wall thickness or material thickness of the fluid disk 9 with respect to the wall thickness or material thickness of the cover plates 7, 8.

In Fig. 2 In this case, the evaporator heat exchanger 1 is shown in the normal operating state in which gas, in particular exhaust gas, flows in the second flow channel 5 and transfers heat to the working medium 2 in the first flow channel 4. For better heat transfer, a rib structure 13 may be arranged in the second flow channel 5, ie between two disk packages 12. A connection of the fluid disk 9 with the two cover plates 7, 8 and also a connection of the rib structure 13 with the respective cover plates 7, 8 takes place preferably cohesively, in particular via a solder joint 14.

In Fig. 3 now a failure of the fluid disk 9 is shown, in which the mean fluid disk 9 is broken and thereby has led to a deformation or an upward bending of the larger-sized cover plate 7. The deformation of the cover plate 7 in turn leads to a loosening of the solder joint 14, whereby the working medium 2 present in the first flow channel 4 can flow into the leakage channel 10. A fluidic connection with the second flow channel 5 and thus with the gas 6 does not take place.

According to the Fig. 4 a case is shown in which the fluid disk 9 is also broken due to an overload and thereby has created a fluidic connection between the second flow channel 5 and the leakage channel 10. The gas 6 passing from the second flow channel 5 can be removed via the leakage channel 10, without interfering with the working medium 2 in the first flow channel 4 to mix. In both shown cases of failure according to the 3 and 4 Thus, an undesired mixing of the working medium 2 with the gas 6 and the resulting difficulties can be reliably avoided.

Looking at the fluid disk 9 according to the Fig. 5 , it can be seen on this very beautiful the first flow channel 4 and the edge extending leakage channel 10 and intervening leakage chambers 11. Also visible is a fluid supply 15 and a fluid discharge 16, via which the fluid disk 9 working medium 2 can be supplied or discharged from this again. Also, the fluid disk 9 has a first opening 17, via which the leakage channel 10 or the leakage chamber 11 with a (leakage) outlet channel 18 (see. Fig. 1 ) are connected. A plurality of oppositely disposed cover plates 7, 8 of two adjacent disk packs 12 additionally each have a second opening 19, wherein between two second openings 19, a leakage bush 20 for forming the outlet channel 18, in particular the leakage outlet channel 18, is arranged. In an assembled disc package 12 thus the first openings 17 are aligned with the second openings 19 and the leakage bushings 20 and thereby form the outlet channel 18th

Looking at the Fig. 6 Furthermore, it can be seen that the cover plates 7, 8 each have a third opening 21 for the passage of the working medium 2 through the first flow channel 4, wherein the third openings 21 between opposite cover plates 7, 8 of two adjacently arranged disc packets 12 respectively a fluid bushing 22 are connected to each other and the fluid bushings 22 have an at least partially circumferential, separated from the first flow channel 4 Fluidbuchsenringkanal 23 which is connected to the leakage channel 10 and / or the leakage chamber 11 of the fluid disk 9 of the disk package 12. This can also be done a backup against from the fluid sockets 22 undesirable emerging working medium 2 are created. The third openings 21 together with the fluid bushes 22 arranged therebetween and the fluid supply 15 or fluid discharge 16 arranged in alignment therewith form a corresponding fluid supply channel 24 or fluid discharge channel 25 in the fluid disks 9.

According to the Fig. 7 is a sectional view through the evaporator heat exchanger 1 according to the invention in the region of the Fluidzuführkanals 24 and the Fluidabführkanals 25 shown. The uppermost fluid bushing 22 is welded to the housing 3 via a welded joint 26 in a fluid-tight manner. Between each two adjacent fluid bushings 22, a disk pack 12 with two cover plates 7, 8 and interposed or soldered fluid disk 9 can be seen.

In Fig. 8 a sectional view through the evaporator heat exchanger 1 according to the invention in the region of the outlet channel 18 is shown, wherein the uppermost leakage bushing 20 in turn welded fluid-tight manner with the housing 3 via a welded joint 26. The individual disk packs 12, in turn consisting of the two cover plates 7, 8 and the fluid disk 9 arranged therebetween, are soldered in a fluid-tight manner both to one another and to the individual leakage bushings 20 via a respective solder joint 14. The uppermost leakage bushing 20 is also referred to as a housing cover bushing 27. At the housing cover bush 27, a further outside the evaporator heat exchanger 1 further line 28 closes (see. Fig. 1 ) into the environment or the periphery. In line 28 or the outlet channel 18, a sensor 29 may be provided which is used to measure the pressure and / or the flow and / or a chemical composition of the fluid in the conduit 28, ie in particular in the leakage channel 10 and in the outlet channel 18th is trained.

Also provided may be a control and / or regulating device 30, which is used to evaluate a signal detected by the sensor 29, in particular the pressure, the flow and / or chemical composition of the fluid, in particular the leakage fluid, in the line 28 and for the control / Control of the working medium conveying and not shown pump or a likewise not shown exhaust gas recirculation valve is formed in response to the detected signal.

Usually the ambient air pressure of approximately 1 bar is applied to the sensor 29, provided that the evaporator heat exchanger 1 is switched off and has ambient temperature. This is according to the Fig. 9 shown by the curve A. If the evaporator heat exchanger 1 is put into operation, the pressure within the line 28 or within the leakage channels 10 increases due to the temperature-induced expansion of the air to about 1 to 1.5 bar, which according to the Fig. 9 is shown with the curve B. If the evaporator heat exchanger 1 is put into operation and the pressure does not rise, which also with the curve A in Fig. 9 is shown, either the sensor 29 is defective or the line 28 and the leakage channel 10 have a leak. In the case of a leak in the fluid disk 9, the pressure increases significantly when the working medium 2 enters the leakage channel 10, which according to the Fig. 9 is shown with the curve C, and slightly less, if the fluid disk 9 tears in the direction of the second flow channel 5 and thus a passage of gas 6 in the leakage channel 10 takes place, which according to the Fig. 9 is shown with the curve D. In general, thus, the operation of the leakage channel 10 can be checked at each restart of the engine or the system, which also a high reliability can be guaranteed. Also, due to the curve can be closed directly on the failure mode.

• Vermeidung einer unerwünschten Vermischung des Arbeitsmediums 2 mit dem Gas 6, beispielsweise Abgas oder Ladeluft,
• keine Gesundheitsgefährdung bei Kältemitteleinsatz,
• kein Sicherheitsrisiko bei Gebrauch von alkoholischem Arbeitsmedium 2,
• laufende Prüfbarkeit der Funktion des Leckagekonzepts.

In general, the evaporator heat exchanger 1 according to the invention has the following advantages:

• Avoidance of undesired mixing of the working medium 2 with the gas 6, for example exhaust gas or charge air,
• no health risk when using refrigerants,
• no safety risk when using alcoholic working medium 2,
• ongoing testability of the function of the leakage concept.

Claims (11)

1. An evaporator heat exchanger (1) for evaporating liquid working medium (2), having a housing (3), in which a first flow channel (4) for conducting the working medium (2) and a second flow channel (5) for conducting a gas (6) are arranged, wherein heat is transferable from the gas (6) to the working medium (2),
   wherein
   the first flow channel (4) is formed by two cover plates (7, 8) and a profiled fluid plate (9) arranged in between,
   wherein the fluid plate (9), together with the two cover plates (7, 8), at the same time delimits at least one leakage channel (10) and/or leakage space (11) that is separated from the two flow channels (4, 5).
2. The evaporator heat exchanger as claimed in claim 1,
   characterized
   in that the at least one leakage channel (10) and/or leakage space (11) is arranged laterally next to or at the periphery of the first flow channel (4).
3. The evaporator heat exchanger as claimed in either of the preceding claims,
   characterized

   - in that the strength of a material of the fluid plate (9) is less than the strength of a cover plate (7, 8) arranged on the fluid plate (9), and/or

   - in that the fluid plate (9) has a smaller wall thickness or material thickness than the cover plates (7, 8) respectively arranged on the fluid plate (9).
4. The evaporator heat exchanger as claimed in one of the preceding claims,
   characterized
   in that in each case two cover plates (7, 8) form a plate pack (12) with a fluid plate (9) arranged in between, said plate pack (12) having at least one, preferably two leakage channels (10) encircling at least partially in the peripheral region.
5. The evaporator heat exchanger as claimed in claim 4, characterized

   - in that the evaporator heat exchanger (1) has a plurality of plate packs (12) stacked on top of one another with in each case a second flow channel (5) arranged in between,

   - in that the leakage channel (10) and/or the leakage space (11) in a fluid plate (9) has a first opening (17),

   - in that a plurality of cover plates (7, 8), arranged opposite one another, of two adjacent plate packs (12) each have a second opening (19), wherein a leakage bushing (20) for forming an outlet duct (18), in particular a leakage outlet duct (18), is arranged between the second openings (19).
6. The evaporator heat exchanger as claimed in claim 5,
   characterized
   in that the first opening (17) is also connected directly to the leakage bushing (20).
7. The evaporator heat exchanger as claimed in one of claims 4 to 6,
   characterized
   in that a plurality of cover plates (7, 8) each have a third opening (21) for conducting the working medium (2) through the first flow channel (4), wherein the third openings (21) are each connected together, between mutually opposite cover plates (7, 8) of two plate packs (12) arranged adjacent to one another, by a fluid bushing (22), and the fluid bushing (22) has an at least partially encircling fluid bushing annular channel (23) that is separated from the first flow channel (4), said fluid bushing annular channel (23) being connected to the leakage channel (10) and/or the leakage space (11) in the fluid plate (9) of the plate pack (12).
8. The evaporator heat exchanger as claimed in claim 6 or 7,
   characterized
   in that the housing (3) has a housing opening which is connected, via a housing leakage bushing (20, 27), to the first and/or second opening (17, 19) in the cover plate (7, 8) of a plate pack (12) arranged adjacent to the housing (3).
9. The evaporator heat exchanger as claimed in claim 8,
   characterized
   in that the housing leakage bushing (27) and all further leakage bushings (20) form the outlet duct (18) for conducting the fluid, wherein a line (28) into the surroundings or periphery is attachable to the housing leakage bushing (27), said line (28) having a sensor (29) which is configured to measure the pressure and/or the flow rate and/or a chemical composition of the fluid in the line (28).
10. The evaporator heat exchanger as claimed in one of claims 4 to 9,
    characterized

    - in that a rib structure (13) is arranged in the second flow channel (5) between in each case two plate packs (12), and/or

    - in that the fluid plate (9) is soldered and/or welded between two cover plates (7, 8).
11. The evaporator heat exchanger as claimed in claim 9 or 10,
    characterized
    in that provision is made of an open-loop and/or closed-loop control device (30) which is configured to evaluate a signal detected by the sensor (29), in particular the pressure, the flow rate and/or the chemical composition of the fluid in the line (28), and for the open-loop/closed-loop control of a pump delivering the working medium (2) and/or of an exhaust gas recirculation valve depending on the signal detected.

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